Disc-type balling device



Jan. 7, 1958 J. C. AGARWAL DISC-TYPE BALLING DEVICE Filed Oct. 27, 1955Angle of repose of ba/led material -M 3 E 3.75'l c I l5'dia.

IN VE N TOR.

his Attorney.

United States Patent 2,818,601 DISC-TYPE BALLING DEVICE Jagdish C.Agarwal, Penn Township, Allegheny County,

Pa., assignor to United States Steel Corporation, a corporation of NewJersey Application October 27, 1955, Serial No. 543,059 2 Claims. (Cl.18-1) This invention relates to an improved disc-type balling device foragglomerating moist fines.

Although my invention is not limited to use with any specific material,it is especially suited for balling fine iron ore or iron mineralconcentrates recovered from beneficiating low grade ores, such astaconite. Often low grade ores must be ground to exceedingly fine sizes(for example 90 percent minus 270 mesh) to liberate the iron mineralsfrom the gangue. A concentrate of this fineness must be agglomeratedbefore it can be utilized for many purposes, such as in a blast furnace,and the agglomerates must possess both substantial mechanical strengthand porosity. One currently known procedure for agglomerating these finematerials involves accreting the moist fines into balls of about to 1inch in diameter, and indurating these balls, commonly on a travelinggrate sintering machine or in a shaft furnace. The balling device can beeither of the disc-type or the drum-type, the present invention beingconcerned with the former. For a discussion of the theories involved inballing, reference can be made to Firth Patent No. 2,411,873, datedDecember 3, 1946. However, as recognized subsequent to this patent, adisc-type balling device produces balls of more uniform size than adrum-type and does so without a circulating load.

Previous disc-type balling devices with which I am familiar haveincluded a fiat circular base plate, an upstanding circumferential rimor weir fixed to this plate, and a power drive for rotating the plateabout its central axis. The plate is supported with its plane inclinedto the horizontal at perhaps 55". This arrangement has severaldisadvantages. The pocket adjacent the bottom juncture of the base plateand rim constitutes a dead space, and the relatively large dead loadunduly increases power required to drive the disc. Partially formedballs or their nuclei within the dead space are subjected to the load ofthe material thereabove. The balls are easily crushed; hence the sizeand capacity of the device is limited by the depth of material whoseweight can be sustained by balls at the bottom of the dead space. Also,only a small portion of the disc surface is utilized effectively forball formation.

Objects of the present invention are to provide an improved disc-typeballing device which eliminates any dead space, permits a greaterportion of the disc surface to be utilized for ball formation, increasesthe capacity, and reduces power requirements.

A more specific object is to provide an improved disctype balling devicein which the disc is a smoothly curved dish whose curvature ismathematically related to the angle of repose of the material balledtherein.

In accomplishing these and other objects of the invention, I haveprovided improved details of structure, a preferred form of which isshown in the accompanying drawing, in which:

Figure 1 is a somewhat diagrammatic vertical sectional view of a ballingdevice constructed in accordance with my invention; and

Figure 2 is a diagrammatic view illustrating the preferred relationbetween the dish curvature in my balling device and the angle of reposeof the material.

My balling device comprises a smoothly and uniformly curved dish ofcircular outline. The dish is journaled to a suitable support 12 torotate on its central axis and is power driven by a motor 13. Since thesupport and drive can be of conventional construction, they are shownonly diagrammatically. A plane tangent to the dish at its central axisslopes at about 40 to to the horizontal, being illustrated as sloping atabout 55. The dish receives moist pulverulent material M to be accretedinto balls, which discharge from the bottom edge. The dish has acontinuously rising curvature from this bottom edge, which is itslowermost point. Consequently there is no dead space below the point ofdischarge. Balls form as their nuclei pick up material while rollingover a moving surface. Nearly half the surface of the dish is utilizedeffectively for this purpose.

Figure 2 shows the preferred relation between the curvature of the dish10 and the angle of repose of the material M. Distance BE represents thelargest diameter, which is governed by the capacity desired. For examplefor a capacity of 50 to tons per hour this diameter can be about 15feet. Distance AB represents the depth, which is determined bymultiplying the tangent of the angle of repose of the balled material(about 35 for iron ore balls) by one fourth to three fourths the largestradius, or preferably two fifths to three fifths this radius. In theexample where the angle of repose is about 35 (tan 35=0.700) and thediameter 15 feet, the depth would be in the following range:

Minimum: 0.700 1.3 feet Maximum: 0.700 X X %:39 feet Next the midpoint Cof line BE is located, and the depth FE diametrically opposite the depthAB is plotted. Finally a circular arc ACF is plotted connecting thepoints A, C and F, and represents the desired curvature.

While I have shown and described only a single embodiment of myinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth, but only by thescope of the appended claims.

I claim:

1. A disc-type balling device adapted to roll moist pulverulent solidsinto balls each about A; to 1 inch in diameter comprising a smoothly anduniformly curved dish of circular outline, means supporting said dishfor rotation about its central axis and with a plane tangent to the dishat its central axis sloping at about 40 to 75 to the horizontal, thelowest point on said dish being located on its outer circumference, thedepth of the dish equalling one-fourth to three-fourths the maximumradius multiplied by the tangent of the angle of repose of the balls,and power means for rotating said dish at a rate which retainspulverulent solids on the dish until they accrete into balls and whichdischarges balls from the bottom portion of the dish.

2. A device as defined in claim 1 having a capacity to roll about 50 to100 tons of pulverulent iron ore per hour into balls, said dish having adiameter of about 15 feet and a depth of about 1.3 to 3.9 feet, thecurvature of the dish being represented by a circular are that connectsthe center with diametrically opposed points on the circumference.

References Cited in the file of this patent UNITED STATES PATENTS2,318,244 McClure May 4, 1943 2,707,304 Haley May 3, 1955 2,726,959Lushbough ct al Dec. 13, 1955 FOREIGN PATENTS 915,072 Germany July 15,1954 98.3 6 Sweden Mar. 16, 1923

